The present invention relates to a planar printed circuit antenna, and in particular to an antenna module working in the ISM (Industry, Science, Medicine) frequency band and assembled in an interior of portable electronic equipment.
A conventional planar printed circuit antenna is disclosed in U.S. Pat. No. 5,708,446. The planar printed circuit antenna is driven by RF signals from a coaxial feed line, and symmetrical transducers are added between symmetrical dipoles to modify the amplitude and phase of the current coming from or going to the dipoles. By this means the antenna can be oriented in a particular direction, and can operate in a designated frequency band. However, symmetrical transducers are not appropriate for use in some antenna systems, such as corner reflection antenna systems. Furthermore, antennas with symmetrical transducers have large profiles and complex structures. Such antennas require additional integrated circuits, and production of them entails much difficulty and complexity.
Referring to FIGS. 6-7 obtained from U.S. Pat. No. 5,708,446, a coaxial feeder element of a conventional planar printed circuit antenna includes an RF cable comprising a conducting core wire 701 and an outer conductor 702. The conducting core wire 701 and outer conductor 702 respectively connect with an upper circuit trace 601 and a lower circuit trace 602 of a printed circuit board (PCB) 60. The PCB is mounted on an insulative substrate 600. The conducting core wire 701 and outer conductor 702 are directly welded to the upper circuit trace 601 and lower circuit trace 602 respectively, and drive the planar printed circuit antenna. The fixed lengths of the conducting core wire 701 and outer conductor 702 restrict the range of the antenna frequency band, and consequently limit the scope of proper operation of the antenna.
For example, a notebook PC with an antenna mounted therein may be used in a variety of different locations. When the notebook PC is moved from one location to another, the environment in the other location may well be different. This can affect the proper functioning of the notebook PC. Thus the frequency band of the notebook computer""s antenna may well have to be altered, to adapt the antenna to the altered environment. Otherwise, the notebook PC may operate improperly or not at all.
The configuration of a conventional antenna mounted in electronic equipment can be modified to operate in a different antenna frequency band. For example, the entire PCB may be replaced with a PCB having a different thickness. However, such modification entails significant downtime and increased costs. Lengthening the antenna to make the syntonous frequency band shift to a lower frequency is a common type of modification. However, this creates difficulties when attempting to design electronic equipment which can be adapted to have its antenna lengthened at a later time. In addition, electronic equipment such as Personal Digital Assistants (PDAs), notebook PCs, mobile phones, and so on are becoming smaller and smaller. Thus the space available in any such equipment for lengthening of an antenna is becoming more and more limited.
Hence, an improved antenna module is desired to overcome the above-mentioned shortcomings of existing wireless network equipment.
A main object of the present invention is to provide a planar printed circuit antenna for use in wireless network devices and having an easily changeable effective frequency band.
Another object of the present invention is to provide an antenna feeder method which can conveniently change the effective frequency band of a wireless network device according to varying needs.
A further object of the present invention is to provide a planar printed circuit antenna which occupies minimal space and which reduces costs.
A planar printed circuit antenna in accordance with the present invention for use in an electronic device comprises a printed circuit board (PCB) mounted on an insulative substrate, a plurality of electronic dipole units, and a coaxial feeder element. The PCB comprises an upper layer, and a lower layer opposite the upper layer and fixed on the insulative substrate. The coaxial feeder element includes an RF cable and a neck securely attached around the RF cable for engaging the coaxial feeder element with the substrate. The RF cable has a conducting core wire,and an outer conductor around the conducting core wire. The conducting core wire is connected to the upper layer via a jumper wire, and the outer conductor is directly connected to the lower layer. Each electronic dipole unit comprises a first and second half dipole respectively arranged on the upper layer and lower layer of the PCB, and respectively coupled to the conducting core wire and the outer conductor. The PCB has space available for accommodating a jumper wire of variable length. The jumper wire has an insulative coating. In cooperation with the free space of the PCB, the jumper wire is adapted to be easily substituted by another jumper wire having a different length, thereby changing an effective frequency band of the antenna.
Other objects, advantages and novel features of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.